1. Field of the Invention
The present invention relates to scalable coding/decoding methods and apparatus used in a still image encoder using wavelet transformation.
2. Description of the Related Art
In a conventional shape information coding method used in a still image encoder using wavelet transformation, pixel information of shapes of all layers output in a process of dividing wavelet must be encoded. In this case, when a scalable coding method is used, the number of pixels to be coded remarkably increases compared with the case where the entire shape information is directly encoded. Accordingly, the efficiency of coding decreases. Also, a system becomes more complicated as the number of pixels to be coded increases. When the size of an input image is large, this effect becomes more pronounced. Accordingly, it takes a long time to restore an overall image.
It is an object of the present invention to provide a still image scalable coding method and an apparatus for dividing a still image into blocks, classifying the divided blocks according to the possibility of using exclusive OR information of each pixel, and encoding the blocks according to classified encoding modes so that arbitrary shape information can be efficiently encoded by a wavelet-based still image encoder.
It is another object of the present invention to provide a decoding method and apparatus corresponding to the wavelet-based still image scalable coding method and apparatus.
It is still another object of the present invention to provide still image coding and decoding methods of dividing an input image having an arbitrary shape into tiles and independently restoring a part of an image desired by a user without a large amount of calculation, from compressed data.
Accordingly, to achieve the first object, there is provided a method of scalably encoding shape information on a still image using a wavelet transformation, comprising the steps of wavelet transforming and scalably encoding shape information on a luminance (Y) component, wavelet encoding texture information on the luminance (Y) component using the shape information on the wavelet transformed luminance (Y) component, padding shape information and texture information on a chrominance (UV) component using the shape information on the luminance (Y) component and texture information on the chrominance (UV) component, wavelet transforming and scalably encoding the padded shape information on the chrominance (UV) component, and wavelet encoding the texture information on the chrominance (UV) component using the shape information on the wavelet transformed chrominance (UV) component.
In a method of scalably encoding shape information on a still image using a wavelet transformation according to the present invention, the steps of scalably encoding the shape information on the luminance (Y) component and scalably encoding the padded shape information on the chrominance (UV) component each comprises the steps of obtaining respective layers by shape adaptive discrete transforming input shape information, encoding the low frequency bandwidth shape information of the lowest shape layer, scalably encoding the low frequency bandwidth shape information of each layer using the low frequency bandwidth shape information of lower layer with respect to each of the shape layers excluding the lowest shape layer, and transmitting the encoded shape information from the lowest layer to uppermost layer.
In a method of scalably encoding shape information on a still image using a wavelet transformation according to the present invention, the step of scalably encoding the low frequency bandwidth shape information of each layer comprises the steps of dividing the low frequency bandwidth shape information of the current layer and the low frequency bandwidth shape information of lower layers into blocks, bordering the respective blocks in the shape information, and determining the encoding mode, performing arithmetic coding on the determined encoding mode, and encoding the bordered block according to the determined encoding modes, with respect to each of the bordered blocks.
In a method of scalably encoding shape information on a still image using a wavelet transformation according to the present invention, when a 1xc3x971 pixel value PL of a binary alpha block (BAB) f1(i, j) of a lower layer corresponds to 2xc3x972 pixel values P0, P1, P2, and P3 of a BAB f2(i, j) of the current layer, the encoding mode is determined to be an interleaved scan line (ISL) mode when all of the following conditions are satisfied with respect to all pixels in the BAB of the lower layers, and the encoding mode is determined to be a raster scan line (RSL) mode when any of the following conditions are not all satisfied.
ondition1=(f2(2i, 2j)==f1(i, j))
ondition2=!(!(f2(2i, 2j)⊕f2(2i+2, 2j)andand(f2(2i+1, 2j)!=f2(2i, 2j))
ondition3=!(!(f2(2i, 2j)⊕f2(2i, 2j+2)andand(f2(2i, 2j+1)!=f2(2i, 2j))
ondition4=!(!(f2(2i+1, 2j)⊕f2(2i+1, 2j+2)andand(f2(2i+1, 2j+1)!=f2(2i+1, 2j)
In a method of scalably encoding shape information on a still image using a wavelet transformation according to the present invention, when the encoding mode is the ISL encoding mode, with respect to each pixel of the block, the step of encoding each bordered block comprises the steps of not encoding P0 when the pixel value to be encoded is P0, calculating context information showing the arrangement of pixels of the current layer around the pixel to be encoded and a probability value for performing arithmetic coding on the pixel to be encoded only when left and right pixel values of the pixel value to be encoded are different from each other and performing the arithmetic encoding on P1 when the pixel value to be encoded is P1, and calculating the context information showing the arrangement of pixels of the current layer around the pixel to be encoded and the probability value for performing the arithmetic coding on the pixel to be encoded only when the pixel values above and below the pixel value to be encoded are different from each other and performing the arithmetic coding on P2 or P3 when the pixel value to be encoded is P2 or P3.
In a method of scalably encoding shape information on a still image using a wavelet transformation according to the present invention, when the encoding mode is the RSL mode with respect to each pixel of the block, the step of encoding each bordered block comprises the steps of not encoding P0 when the pixel value to be encoded is P0 and the corresponding PL is 0, calculating the context information showing the arrangement of pixels of the current layer and lower layers around the pixel to be encoded and the probability value for performing the arithmetic coding on the pixel to be encoded and performing the arithmetic coding on P0 when the pixel value to be encoded is P0 and the corresponding pixel value PL is not 0, and calculating the context information showing the arrangement of the pixels of the current layer and the lower layers around the pixel to be encoded and the probability value for performing the arithmetic coding on the pixel to be encoded and performing the arithmetic coding on P1, P2, or P3 when the pixel value to be encoded is P1, P2, or P3.
There is provided a method of scalably encoding shape information on a still image using a wavelet transformation, comprising the steps of wavelet transforming the shape information on the luminance (Y) component by an even symmetry wavelet filter and scalably encoding the shape information on the luminance (Y) component, wavelet encoding the texture information on the luminance (Y) component using the shape information on the wavelet transformed luminance (Y) component, and wavelet encoding the texture information on the chrominance (UV) component using the shape information on the wavelet transformed luminance (Y) component.
In a method of scalably encoding shape information on a still image using a wavelet transformation according to the present invention, the step of padding the shape information and texture information on the chrominance (UV) component comprises the steps of obtaining downsampled shape information from shape information on the luminance (Y) component for compensating for the chrominance (UV) component of 4:2:0 or 4:2:2, dividing the downsampled shape information into blocks corresponding to the number of layers and extending the shape information to a region including all pixels of boundary blocks which are partially comprising the shape respectively, and obtaining texture information corresponding to the extended region by padding the texture information on the chrominance (UV) component in the horizontal and vertical directions.
To achieve the second object, there is provided a method for scalably decoding encoded shape information on a still image using wavelet transformation, comprising the steps of scalably decoding and wavelet transforming the encoded shape information on the luminance (Y) component, wavelet decoding the encoded texture information on the luminance (Y) component using the shape information on the wavelet transformed luminance (Y) component, scalably decoding and wavelet transforming the encoded shape information on the chrominance (UV) component, and wavelet decoding the encoded texture information on the chrominance (UV) component using the shape information on the wavelet transformed chrominance (UV) component wavelet transformed.
In a method for scalably decoding encoded shape information on a still image using wavelet transformation according to the present invention, the steps of wavelet transforming the encoded shape information on the luminance (Y) component and wavelet transforming the encoded shape information on the chrominance (UV) component each comprise the steps of receiving encoded shape information from the lowest layer to uppermost layer, obtaining the low frequency bandwidth shape information of the lowest layer by decoding the encoded shape information of the lowest layer, scalably decoding the low frequency bandwidth shape information by decoding the encoded shape information of each layer using the low frequency bandwidth shape information of lower layers with respect to the respective layers excluding the lowest layer, and obtaining the respective layers by shape adaptive discrete wavelet transforming the low frequency bandwidth shape information of the decoded respective layers.
In a method for scalably decoding encoded shape information on a still image using wavelet transformation according to the present invention, the step of scalably decoding the low frequency bandwidth shape information comprises the steps of receiving encoded shape information and dividing the shape information of the current shape layer and the shape information of the lower layers into blocks, bordering the respective blocks in the shape information, and performing arithmetic decoding on the encoding modes of the respective bordered blocks and decoding the encoded shape information in each block according to the decoded encoding mode.
In a method for scalably decoding encoded shape information on a still image using wavelet transformation according to the present invention, when a 1xc3x971 pixel value PL of a binary alpha block (BAB) f1(i, j) of a lower layer corresponds to 2xc3x972 pixel values P0, P1, P2, and P3 of a BAB f2(i, j) of the current layer, the encoding mode is determined to be an interleaved scan line (ISL) mode when all of the following conditions are satisfied with respect to all pixels in the BAB of the lower layers and the encoding mode is determined as a raster scan line (RSL) mode when any of the following conditions are not satisfied.
ondition1=(f2(2i, 2j)==f1(i, j))
ondition2=!(!(f2(2i, 2j)⊕f2(2i+2, 2j)andand(f2(2i+1, 2j)!=f2(2i, 2j))
ondition3=!(!(f2(2i, 2j)⊕f2(2i, 2j+2)andand(f2(2i, 2j+1)!=f2(2i, 2j))
ondition4=!(!(f2(2i+1, 2j)⊕f2(2i+1, 2j+2)andand(f2(2i+1, 2j+1)!=f2(2i+1, 2j)
In a method for scalably decoding encoded shape information on a still image using wavelet transformation according to the present invention, when the encoding mode is the ISL encoding mode, with respect to each pixel of the block, the step of decoding the encoded shape information in each block comprises the steps of restoring P0 by PL when the pixel value to be decoded is P0, restoring P0 by the pixel value to the left or right of the pixel value to be decoded when the pixel value to be decoded is P1 and the pixel values to the left and right of the pixel value are equal to each other, and calculating the context information showing the arrangement of the pixels of the current layer around the pixel to be decoded and the probability value for performing the arithmetic decoding on the pixel to be decoded and performing the arithmetic decoding on P1 when the pixel value to be decoded is P1 and the pixel values to the left and right of the pixel value to be decoded are different from each other, and decoding P2 or P3 by the pixel value above or below the pixel value to be decoded when the pixel value to be decoded is P2 or P3 and the pixel values above or below the pixel value are equal to each other and calculating the context information showing the arrangement of the pixels of the current layer around the pixel to be encoded and probability value for performing arithmetic decoding on the pixel to be decoded and performing arithmetic decoding on P2 or P3 when the pixel value to be decoded is P2 or P3 and the pixel values above and below the pixel value are different from each other.
In a method for scalably decoding encoded shape information on a still image using wavelet transformation according to the present invention, when the encoding mode is the RSL encoding mode, with respect to each pixel of the block, the step of decoding the encoded shape information in each block comprises the steps of restoring P0 by 0 when the pixel value to be decoded is P0 and the corresponding PL is 0, calculating the context information showing the arrangement of the pixels of the current layer and the lower layers around the pixel to be decoded and the probability value for performing the arithmetic decoding on the pixel to be decoded and performing the arithmetic decoding on P0 when the pixel value to be decoded is P0 and the corresponding PL is not 0, and calculating the context information showing the arrangement of the pixels of the current layer and the lower layers around the pixel to be decoded and the probability value for performing the arithmetic decoding on the pixel to be decoded and performing the arithmetic decoding on P1, P2, or P3 when the pixel value to be decoded is P1, P2, or P3.
To achieve the third object, there is provided an apparatus for scalably encoding shape information on a still image using wavelet transformation, comprising a shape information scalable encoder for wavelet transforming and scalably encoding the shape information of a luminance (Y) component and a chrominance (UV) component, a chrominance (UV) image shape/texture padding unit for padding shape information and texture information of a chrominance (UV) component using shape information of a luminance (Y) component and texture information of a chrominance (UV) component with respect to 4:2:0 or 4:2:2 shape information, and a texture information wavelet encoder for wavelet encoding the texture information of the luminance (Y) component and the chrominance (UV) component using the shape information wavelet transformed by the shape information scalable encoder.
In an apparatus for scalably encoding shape information on a still image using wavelet transformation according to the present invention, the shape information scalable encoder comprises a luminance (Y) shape scalable encoder for wavelet transforming and scalably encoding the shape information of the luminance (Y) component and a chrominance (UV) shape scalable encoder for wavelet transforming and scalably encoding the shape information of the chrominance (UV) component padded by the chrominance (UV) image shape/texture padding unit.
In an apparatus for scalably encoding shape information on a still image using wavelet transformation according to the present invention, the luminance (Y) shape scalable encoder and the chrominance (UV) shape scalable shape encoder each comprises a plurality of shape adaptive discrete wavelet transformers for receiving shape layers and generating the shape layers of lower layers, a shape encoder for encoding the low frequency bandwidth shape information of the lowest shape layer, a plurality of scalable encoders for scalably encoding the low frequency bandwidth shape information of the respective layers using the low frequency bandwidth shape information of the lower layers with respect to the respective shape layers excluding the lowest shape layer, and a multiplexer for transmitting the encoded shape information from the lowest layer to the upper layers.
In an apparatus for scalably encoding shape information on a still image using wavelet transformation according to the present invention, each scalable encoder comprises means for dividing the low frequency bandwidth shape information of the current layer and the low frequency bandwidth shape information of the lower layers into blocks, means for bordering the respective blocks in the shape information, means for determining the encoding mode according to the possibility of using exclusive OR information of each pixel in the bordered block, means for scanning the respective pixels in a block in the ISL order and omitting encoding the pixels when exclusive OR information can be used and obtaining the context information and performing the arithmetic coding on the pixels when the exclusive OR information cannot be used, when the encoding mode is the ISL encoding mode, and scanning the respective pixels in a block in the RSL order, obtaining the context information and performing the arithmetic coding on the pixels when the encoding mode is the RSL encoding mode.
To achieve the third object, here is provided an apparatus for scalably decoding encoded shape information on a still image using wavelet transformation, comprising a shape information scalable decoder for scalably decoding and wavelet transforming the encoded shape information on the luminance (Y) component and the chrominance (UV) component and a texture information wavelet decoder for wavelet decoding encoded texture information on the luminance (Y) component and the chrominance (UV) component using the shape information wavelet transformed by the shape information scalable decoder.
In an apparatus for scalably decoding encoded shape information on a still image using wavelet transformation according to the present invention, the shape information scalable decoder comprises a luminance (Y) shape scalable decoder for scalably decoding and wavelet transforming the encoded shape information on the luminance (Y) component and a chrominance (UV) shape scalable decoder for scalably decoding and wavelet transforming the encoded shape information on the chrominance (UV) component.
In an apparatus for scalably decoding encoded shape information on a still image using wavelet transformation according to the present invention, the luminance (Y) shape scalable decoder and the chrominance (UV) shape scalable shape decoder each comprises a demultiplexer for distributing the encoded shape information from the lowest layer to upper layers, a shape decoder for obtaining the low frequency bandwidth shape information of the lowest layer by decoding the encoded shape information of the lowest shape layer, a plurality of scalable decoders for scalably decoding the low frequency bandwidth shape information by decoding the encoded shape information of the respective layers using the low frequency bandwidth shape information, with respect to the respective shape layers excluding the lowest shape layer, and a plurality of shape adaptive discrete wavelet transformers for obtaining each of the shape layers by shape adaptive discrete wavelet transforming the decoded low frequency bandwidth shape information of the respective layers.
In an apparatus for scalably decoding encoded shape information on a still image using wavelet transformation according to the present invention, each scalable decoder comprises means for receiving encoded shape information and dividing the shape information of the current layer and the shape information of the lower layers into blocks, means for bordering the respective blocks in the shape information, means for performing arithmetic decoding on the encoding mode determined according to the possibility of using the exclusive OR information of the respective pixels in the bordered block, means for scanning the respective pixels in a block in the ISL order decoding and decoding the pixels by exclusive OR information when the exclusive OR information can be used and obtaining the context information and performing the arithmetic decoding on the pixels when the exclusive OR information cannot be used, when the encoding mode is the ISL encoding mode, and means for scanning the respective pixels in a block, obtaining the context information, and performing the arithmetic decoding on the pixels, when the encoding mode is the ISL encoding mode.
To achieve the third object, there is provided a method for scalably encoding a still image using wavelet transformation, comprising the steps of dividing an input object having an arbitrary shape into tiles having a uniform size and classifying a control component, encoding a control signal with respect to each tile, wavelet transforming shape and texture information, scalably encoding the values of the respective layers, and encoding object information in a tile, with respect to each tile, and sequentially connecting encoded bit streams with respect to each tile.
To achieve the third object, there is provided a method for decoding a bit stream obtained by scalably encoding a still image using wavelet transformation, comprising the steps of receiving encoded bit stream, dividing the encoded bit stream into objects and classifying a control component from a plurality of tile components in bit streams with respect to the respective objects, decoding the control component, scalably decoding shape and texture information and decoding object information in a tile, with respect to each tile component, composing the object information items decoded with respect to the respective tile components using the decoded control component in each object, and composing a plurality of object information items on a screen.
To achieve the third object, there is provided an apparatus for scalably encoding a still image using wavelet transformation, comprising one or more tile dividers dividing an input object having an arbitrary shape into tiles having a uniform size and classifying control components, one or more control signal encoders for encoding control components classified by the tile dividers, a plurality of image encoders for receiving tiles divided by the tile dividers, wavelet transforming shape and texture information in the tiles, and scalably encoding the values of the respective layers, and a multiplexer for sequentially connecting encoded bit streams to the respective tiles.
To achieve the third object, there is provided an apparatus for decoding a bit stream obtained by scalably encoding a still image using wavelet transformation, comprising a demultiplexer for receiving the encoded bit stream, dividing the encoded bit stream into objects, and classifying a control component and a plurality of tile components in the bit stream with respect to each object, one or more control signal decoders for decoding the control component, a plurality of still image decoders for receiving a tile component and scalably decoding shape and texture information in the tile, one or more tile compositors for composing the decoded tile component in each object, and an object compositor for composing a plurality of object information items composed by the tile compositor on a screen.